Strain and a novel process for ethanol production from lignocellulosic biomass at high temperature

Abstract

The present invention relates to a novel thermophilic ethanol producing yeast strain, a microorganism, Kluyveromyces sp. IIPE453 MTCC 5314, classified as yeast, which exhibits growth and sugar fermentation at higher temperature range between 37° C. to 55° C. The novel yeast strain is capable of utilizing wide range of mono and di-saccharide sugars belongs to hexose and pentose carbohydrate family individually or in a mixture that obtained from hydrolysis of lignocellulosic biomass, such as sugarcane bagasse or starch based biomass such as cassava, potato, corn etc. for its growth and produce ethanol by fermentation process at temperature range 40° C. to 55° C. It also relates to a novel process for the preparation of ethanol by Kluyveromyces species IIPE453. Thus application of thermophilic yeast strain Kluyveromyces sp. IIPE453 MTCC 5314 has wide scope for industrial production of bioethanol from low cost renewable biomass as alternate feedstock to molasses.

1. A process for the preparation of ethanol by Kluyveromyces species IIPE453 MTCC 5314, comprising the steps:
 (a) culturing the strain Kluyveromyces species IIPE453 MTCC 5314 in salt medium 1 (SM1) wherein the said SM1 comprising 0.15 g/l di-sodium hydrogen ortho-phosphate, 0.15 g/l potassium di-hydrogen ortho-phosphate, 2.0 g/l ammonium sulphate, 1.0 g/l yeast extract and 10 g/l glucose with pH in the range of 5.0 to 6.5 at a temperature in the range of 37° C. to 55° C. for a period of 24 to 30 hours under stirring to obtain cell biomass; 
 (b) inoculating the cell biomass as obtained in step (a) in fresh salt medium 2 (SM2) wherein the said SM2 comprises 0.15 g/l di-sodium hydrogen ortho phosphate, 0.15 g/l potassium di-hydrogen ortho phosphate, 1.0 g/l ammonium sulphate, 1.0 g/l yeast extract supplemented with 50 to 100 g/l of a fermentable substrate selected from the group consisting of monosaccharide and disaccharide sugars, bagasse, hydrolysate of lignocellulosic biomass, starch based biomass, either singly and in any combination thereof and with pH in the range of 3.5 to 6.5 at a temperature in the range of 45° C. to 60° C. for a period of 24 to 48 hours under stirring to obtain fermentation broth containing ethanol; or 
 (c) immobilizing the cell biomass as obtained in step (a) onto bagasse chips and inoculating the immobilized biomass in fresh salt medium 2 (SM2) wherein the said SM2 comprises 0.15 g/l di-sodium hydrogen ortho phosphate, 0.15 g/l potassium di-hydrogen ortho phosphate, 1.0 g/l ammonium sulphate, 1.0 g/l yeast extract supplemented with 50 to 100 g/l of a fermentable substrate with pH in the range of 3.5 to 6.5 at a temperature in the range of 45° C. to 60° C. for a period of 40 to 90 hours under stirring to obtain fermentation broth containing ethanol; and 
 (d) separating the ethanol from the fermentation broth. 
 
     
     
       2. The process according to  claim 1 , wherein the sugars are selected from the group consisting of glucose, maltose, xylose, sucrose and starch. 
     
     
       3. The process according to  claim 1 , wherein the concentration of fermentable substrate sugar in the medium SM2 is about 100 g/l. 
     
     
       4. The process according to  claim 1 , wherein the temperature of fermentation in step (b) is about 50 degree C. 50° C. to 55° C. 
     
     
       5. The process according to  claim 1 , wherein the pH in step (b) ranges from about 5.5 to about 6.0. 
     
     
       6. The process according to  claim 1 , wherein the productivity of ethanol ranges from about 0.78 to about 13.8 grams per liter per hour. 
     
     
       7. The process according to  claim 1 , wherein the yield of ethanol ranges from 10 to about 58.75%. 
     
     
       8. The process according to  claim 1  wherein the separation of ethanol from fermentation broth in step (d) in done by a process selected from the group consisting of distillation, pre-evaporation and filtration.